Moving laser beam readers or laser scanners, as well as solid-state imaging systems or imaging readers, have both been used, in both handheld and hands-free modes of operation, to electro-optically read bar code symbols having different bar and space patterns that are used to represent different characters. Sets of these patterns are grouped together to form a symbology. There are many types of bar code symbologies, each having their own special characteristics and features. Most symbologies are designed to meet the needs of a specific application or industry. One omnipresent symbology is the Universal Product Code (UPC) Version A (UPC-A) symbol, which is comprised of a linear or one-dimensional arrangement of bars and spaces (each termed as an element) of different light reflectivities and of various widths that, when decoded, uniquely identify a product and its manufacturer.
The moving laser beam reader generally includes a laser for emitting a laser beam, a focusing lens assembly for focusing the laser beam to form a beam spot having a certain size at a focal plane in a range of working distances, a scan component for repetitively scanning the beam spot across a symbol in a scan pattern, for example, one or more scan lines, across the symbol multiple times per second, e.g., forty times per second, a photodetector for detecting return light reflected and/or scattered from the symbol and for converting the detected return light into an analog electrical signal, and signal processing circuitry including a digitizer for digitizing the analog signal, and a microprocessor for decoding the digitized signal based upon a specific symbology used for the symbol.
The imaging reader generally includes a solid-state imager or sensor having an array of cells or photosensors, which correspond to image elements or pixels in a field of view of the imager, an illuminating light assembly for illuminating the field of view with illumination light from an illumination light source, e.g., one or more light emitting diodes (LEDs), and an imaging lens assembly for capturing return ambient and/or illumination light scattered and/or reflected from the symbol being imaged over a virtual scan pattern over a range of working distances. Such an imager may include a one- or two-dimensional charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) device and associated electronic circuits for producing electronic analog signals corresponding to a one- or two-dimensional array of pixel information over the field of view. Again, signal processing circuitry including a digitizer is used for digitizing the analog signal, and a microprocessor is used for decoding the digitized signal based upon a specific symbology used for the symbol.
As advantageous as both types of readers are in reading symbols, it is desirable in many applications for each reader to read symbols of different polarities, i.e., “normal” codes and “inverse” codes, and to obtain the same decoded result no matter the symbol polarity. A “normal” (or regular or direct) code is a code where the bars are of less light reflectivity than the background, which background includes the spaces between the bars (e.g., black/dark bars on a white/light background). An “inverse” code is a code where the bars are more reflective than the background on which they are disposed including the spaces therebetween (e.g., white/light bars on a black/dark background). Although symbols are normally printed on products as normal codes, some product manufacturers insist on printing the symbols as inverse codes due to the nature of the product and its packaging.
For most symbologies, including the UPC-A symbology described above, the reader can detect whether the symbol is a normal or an inverse code, for example, by evaluating the reflectivity of the right and left outer margins disposed at opposite ends of the code. Once the reader knows what type of code polarity is being read, the microprocessor can properly set the digitizer to digitize the code with the correct polarity, and properly decode the symbol with the correct polarity setting.
However, not all symbologies have such margins. For example, the GS1 Databar Code family is a recent barcode symbology for space-constrained identification from GS1. Databar codes have been utilized to solve many problems in point-of-sale, grocery and healthcare, applications, where products are too small to allow for traditional UPC-A symbols, or where additional information needs to be encoded. In the Databar family, the Databar-14 symbol is a 14-digit data structure comprised of a linear arrangement of bars and spaces (each termed as an element) of different light reflectivities and of various widths that, when decoded, uniquely identify a product and its manufacturer. In addition, GS1 DataBar Expanded is an analogous, but longer, bar-and-space data structure that can encode additional information, such as sell-by or expiration date, product weight, country of origin, serial number, and lot number, and is seeing increased use in manufacturers' coupons. Thus, the Databar symbol family is designed to replace or expand use of the UPC-A symbol, as well as to provide additional information and, thus, provides for greater product identification, traceability, quality control, and more flexible coding for coupon applications.
Yet, as advantageous as the Databar-14 and the Databar Expanded symbols have become, they do not have the aforementioned left and right outer margins and, thus, their polarity cannot be determined by the readers in the same manner as that described above for UPC-A symbols. As best shown in FIG. 3, the Databar-14 structure is composed of two data blocks or segments, each containing a 5-element finder pattern and two adjacent data characters. The left finder pattern contains a space-bar-space-bar-space sequence, while the right finder pattern contains a bar-space-bar-space-bar sequence. There are nine finder pattern variants, all valid for each of the left and right finder patterns. The Databar Expanded structure can be of variable length ranging from two blocks or segments to eleven blocks or segments. The exemplary Databar Expanded structure shown in FIG. 4 is composed of three data blocks, each containing a 5-element finder pattern and two adjacent characters. An A1 finder pattern and a B1 finder pattern each contains a space-bar-space-bar-space sequence, while a B2 finder pattern contains a bar-space-bar-space-bar sequence.
One concern for a reader that is capable of reading both normal and inverse Databar-14 or Databar Expanded symbols is that a symbol misdecode or misread may occur, because of confusion between the finder patterns, and the lack of an outer margin to determine the symbol polarity. More specifically, the right finder pattern is, by design, already the inverse of the left finder pattern in the Databar-14 symbol of FIG. 3. Thus, without knowing the polarity, the reader may interpret the right finder pattern as the left finder pattern, or vice versa, and, as a result, a different incorrect code will be read. Analogously, the B2 finder pattern in the Databar Expanded symbol of FIG. 4 is, by design, already the inverse of the A1 finder pattern or the B1 finder pattern, and, hence, may be interpreted as the A1 finder pattern or the B1 finder pattern, or vice versa, and, as a result, a different incorrect code will again be read.
Once it was revealed that Databar-14 or Databar Expanded symbols could be interpreted and decoded differently when printed as normal or inverse codes, the prior art made the printing of inverse Databar symbols of any variant illegal. In response, many reader manufacturers disabled the ability to decode inverse Databar symbols. However, this was an unsatisfactory solution, because some customers still insist on printing both normal and inverse Databar symbols and fully expect that their readers should be able to read them.
Accordingly, there is a need for an arrangement for, and a method of, enabling such normal and inverse codes to both be printed, and to enable such readers to read both normal and inverse codes to satisfy customer expectations, while preventing misdecodes of such Databar symbols in such readers.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The arrangement and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.